Photographic process, product and apparatus



March 28, 1961 PHOTOGRAPHIC PROCESS, PRODUCT AND APPARATUS Filed 001',- 9. 1956 E. LAND 2 Sheets-Sheet l FIG. 3

Suppor'l' Subcoa+ Image Receiving Layer S'l'ripping Layer Emulsion Layer Fluid Reagen'l' Rigid Plal'e Fluid Reagenr mulsion Shipping Layer Layer Image ubcoa+ $uppor+ An'l'i -Hala+ion Receiving Layer Layer UYgNTOR.

wle I wz w ATTQRNEYS March 28, 1961 LAND 2,977,226

PHOTOGRAPHIC PROCESS, PRODUCT AND APPARATUS Filed Oct. 9. 1956 2 Sheets-Sheet 2 Jim i 6| 5 i z s e I In "111",. IIIIIIIIIIIIIYIIZ 7 W W m "III I III! ATTORNEYS Unit d S te Pamll PHOTOGRAPHIC PROCESS, PRODUCT LAND APPARATUS Filed Oct. 9, 1956, Ser. No. 614,983

7 Claims. (Cl. 96-3) This invention relates to photography and, more particularly, to improved methods for treating photosensitive materials with fluid processing reagents and to film units and apparatus for use inthe performance of said methods.

A variety of photographic processes have been proposed which are accomplished by a fluid processing reagent spread in a thin layer between an area of a photosensitive material and the surface of another element superposed therewith. Generally, these processes result in the production of visible images accomplished by the transfer of image-providing substances from the photosensitive material to another layer located in superposi tion therewith. In many of these, processes, particularly wherein two or more photosensitive sheet materials are exposed and treated to produce two or more images, it may be desirable to spread at least two different fluid reagents simultaneously on exposed areas of at least two photosensitive sheets, preferably located superposed relation and separated by an intervening layer, to produce at least two images in separate layers.

Objects of the present invention are: to provide a novel method for simultaneously treating at least two superposed photosensitive material layers' with at least two fluid processing reagents, which method is characterized by the fact that one of the fluid reagents is spread in a layer on one of the photosensitive layers simultaneuosly with the spreading of the other reagent on the other photosensitivelayer and the photosensitive layers and reagents are isolated from one another during spreading and during the processing reactions instituted thereby, to pro.- vide a novel method of the foregoing type wherein spreading of the fluid reagents is eflected by movement of the photosensitive layers in superposed relation between a pair of pressure-applying members and whereby an accurate control may be had over the thickness of each layer of fluid reagent spread on one of the photosensitive layers; and to provide a novel method of the foregoing type wherein at least two layers of fluid are spread on opposite sides of a substantially rigid sheetlike element located between and in superposition with a pair of photosensitive layers located on flexible support sheets.

The methodof the present invention finds particular application in a number of photographic processes, such as color processes involving the formation of two or i more positive images, wherein it is desirable to simultaneously expose at least two different photosensitive layers while the photosensitive layers are maintained in intimate face-to face contact, to separate the photosensitive layers during treatment, which results in the production of positive images in separate layers, and'thereaftersuperposing the image-carrying layers in face-to-face contact with the images in registrationwhereby theimages maybe viewed in conjunction with one another. V Other objects of the invention'are': to provide a novel method wherein at least'twophotosensitive layers, each located in superposition with an image-receiving layer and secured to the other photosensitive, layeran'd superposed 2,977,226 Patented Mar. 28, 1961 image-receiving layer, are located in intimate face-toface contact and simultaneously exposed to produce different records of a subject, and including the steps, performed while maintaining said photosensitive and imagereceiving layers secured together, of treating each of said photosensitive layers to produce apositive image in each image-receiving layer from the photosensitive layer superposed therewith, separating said photosensitive layers from said image-receiving layers, and superposing said image-receiving layers in intimate face-to-face contact, at least one of said image-receiving layers being transparent to permit the viewing of said positive images in conjunction with one another; and to providea method as described above wherein the treatment of said photosensitive layers is efiected by a layer of fluid reagent spread between each photosensitive layer and the surface of another element superposed therewith while said photosensi tive layers are in superposed; relation.

A further object of the invention is to provide photographic products and apparatus adapted to be employed in the foregoing methods. A

Other objects of the invention will, in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relation and order of one or more of such steps with respect to each of the others, the product possessing the features, properties and the relation of elements, and the apparatus possessing the construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims. p For a fuller understanding of the nature and objects of'the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein: b

Figure 1 is a schematic enlarged sectional view of a photographic assemblage adaptedto be employed in the Fig.- 5 is a schematic enlarged elevational view, par-v tially in section, illustrating? one stage in carrying out the process of the invention; and i Fig. 6 is an enlarged schematic elevational view, partially in section, illustrating another embodiment of the invention and showing one stage in carrying out the process of the invention.

a The method and apparatus of the herein disclosed in: vention find utility in the treatment of photosensitive sheet materials, and particularly materials comprising a layer of light-sensitive material, such as a silver halide emulsion, carried on a flexible'support sheet, for example of paper, organic plastic material and the like. Processing of the photosensitive material is effected by a fluid reagentdis:

tributed in a'thin layerbetween the photosensitive material and the surface of another element, preferably in the form of a second sheet, by movement of the two sheets in superposed relation between a pair of pressure-apply; ing members. The second sheet may serve merely to aid in the spreading of theprocessing agent or it may serve other functions; for example, it may be provided with additional reagents which participate in a processing reaction or it mayserve as a support for image-forming substances transferred from the photosensitive material duringprocessing, The fluid processing reagent maybe provided and distributed between'the sheets in a number of ways, shown and described, for example, in Patent No. 2,647,056, issued July 28, 1953, to Edwin H. Land. Preferably the fluid agent is provided in a rupturable podlike container located between the photosensitive and second sheets adjacent an edge of the area of the photosensitive sheet over which the fluid is to be distributed so that, as the two sheets are moved between the pressure-applying members, the container is first to be subjected to compressive forces for causing its fluid contents to be discharged between the sheets. Continued movement of the sheets between the pressure-applying members is then effective to distribute the fluid in a thin layer between adjacent surfaces of the two sheets. To permit a more uni.- form and controlled spreading of the fluid in the container, there is provided in the fluid a material which imparts thereto a predetermined high viscosity. A further control may be had over the uniformity and thickness of the layer of fluid, as described in Patent No. 2,543,160, issued February 27, 1951, to Murry N. Fairbank, by pro viding pressure-applying members having fluid-spreading surfaces and cooperating portions on one of the members adapted to engage the margins of the two sheets and maintain the fluid-spreading surfaces spaced apart a predetermined amount greater than the thickness of the margins of the two sheets. By providing means for spacing the fluid-spreading surfaces of the pressure-applying members apart, the effect on the thickness and uniformity of the fluid layer, due to variations in the thickness of the sheets, the viscosity of the fluid, the pressure applied, and the speed at which the sheets are moved, is minimized or entirely eliminated.

As previously mentioned, a number of photographic Wrasse. p

processes may be performed which require at least two photosensitive materials arranged in separate layers and located in superposed relation, although not necessarily in contact with one another. It may be desirable to process each of these two layers with a separate fluid reagent while maintaining the layers in superposed relation and to effect the spreading of the two fluid reagents on the photosensitive layers simuitaneously. Hithertofore this has been accomplished by superposing each photosensitive layer or sheet with the surface of a second sheet, which surfaces may be the opposite surfaces of .the'same sheet, and moving the sheets in superposition between a pair of pressure-applying members. This arrangement, while essentially satisfactory, is not, howeveryconducive to ac ra e con rol o er the. hi kne s or uniformity of e o l y rs of fluid sp ea etween the heets. since pressure is applied through at least three layers ofshect material and two layers of fluid, all of which may vary in thickness and because there may be variations and dif. ferences'in the viscosities of the two fluids and the speed at which the sheets are moved between the pressureapplying, members. Additionally, the compressive pressure exerted on one side of each pair of sheets and layer of fluid therebetween must first be transmitted through the other layer of fluid and at least one other sheet, with the result that the compressive pressure applied to each layer of fluid and the hydraulic pressure generated therei in may be subjected to uncontrollable fluctuations resulting in variations. in the thicknessof the other layer of fluid. It becomes apparent that the mere provision of cooperating portions on one of the pressure-applying members would be of little; help in assuring accurate control over the thickness and uniformity of the spread of the two layers of fluid, especially when the sheet, or sheets, located intermediate the two photosensitive sheets is flexible.

The present invention comprehends a method whereby at l st two fl i proc g r g may b spr d simultaneously in two separate and distinct layers of accu; rately predetermined uniform thickness on and between adjacent and coextensive areas of two flexible photosensia tive sheet materials by movement of said sheet materials in superposed relation between a pair of pressure-applying members. This is accomplished, in a preferred form of invention, by providing a substantially rigid flat sheetlike element or plate between the two superposed photosensitive sheets and moving the sheets and intervening plate in superposition between a pair of pressure-applying members each having cooperating portions for engaging the margins of the sheets and maintaining the fluid-spreading surfaces of the pressure-applying members spaced apart by an amount predeterminedly exceeding the combined thickness of the margins of the photosensitive sheets and intervening rigid element. Each surface of the intervening plate functions in the nature of one of a pair of fluidspreading surfaces and cooperates with the fluid-spreading surface of one of the pressure-applying members for insuring an even, controlled spread of fluid in a layer between the surface of the plate and a superposed photosensitive sheet. The plate is sufliciently rigid and inflexible so that it cannot be readily deformed due to hydraulic pressure generated in the layers of processing fluid, with the result that the pressures exerted on each layer of fluid and generated therein are substantially equal to the pressures exerted on and generated in the other layer, and the gaps or spaces between the surfaces of the rigid plate and the photosensitive elements are accurately and uniformly controlled and maintained.

In a preferred form of the invention, each of the pressure-applying members includes cooperating portions for engaging one of the superposed photosensitive sheets adjacent the opposite edges thereof and the pressure-applying members include fluid-spreading portions located be tween the edge-engaging portions having cooperating converging fluid-spreading surfaces at least one of which is preferably convexedly curved. At least one of the pressure-applying members is movably mountedfor movement toward and away from the other member and means are provided for resiliently urging the movably mounted member toward the other member under a force greater than the force produced by the pressure generated in the fluids during spreading thereof. The edge-engaging portions are so related to the members as to space the converging fluid-spreading surfaces apart a predetermined distance greater than the spacing existing between said edge-engaging portions when the latter are operatively associated. These latter portions are operative to move the movable pressure-applying member to cause the ,spac ing of the fluid-spreading surfaces to increase upon any increase in the thickness of the photosensitive sheets or intervening plate, and allows said resilient means to move 1 said member to decrease the spacing of said surfaces upon any decrease in thickness of said sheets. This ar-v rangement of the portions of the pressure-applying members permits separation of the two sheets and intervening plate as they are advanced between the fluid-spreading surfaces which are independent of the thicknesses of the sheets and plate. The sheet-engaging portions of the pressure-applying members preferably constitute a pair of shoulders on eachmember cooperating with corresponding shoulders on the opposite member. The shoulders extend beyond the-fluid-spreading surface of each member toward the other member to engage marginal superposed edges of the two sheets and the intervening plate as the sheets and plate pass'between the fluidspreading surfaces. and thus predeterminedly space the fluid-spreading surfaces apart from one another a predetermined amount greater than the combined edge thickness of said sheets and said plate, and space each of said fluid-spreading surfaces apart from the surface of the intervening plate a predetermined amount greater than the edge thickness of the photosensitive sheet located between said member and said plate. In another form of the invention, edge-engaging shoulders may .beprovided on either or both surfacesof the intervening plate fo pacing he fluidspreading surface of a pressure-applying member apart from the surfaceot the plate a pre S determined amount greater than the edge thickness of the photosensitive sheet located therebetween.

While the method of the inventionrnay be employed to effect a variety of photographic processes wherein it is desired to expose and treat at least two photosensitive layers to produce at least two positive images adapted to be viewed in conjunction with one another, it is particularly useful in the production of positive photographic prints comprising at least two colored images. Many processes of this type, with which the method of the present invention finds particular utility, may occur to persons skilled in the For purposes of illustration, however, the present invention is described in connection with the production of a positive photographic print comprising at least two dye images formed by exposing two silver halide emulsion layers while the layers are held in intimate face-to-face contact, to produce two diiferent records of a subject; and thereafter treating the exposed emulsion layers with two fluid reagents for producing, in different image-receiving layers superposed with said emulsion layers, two dye images, andthereafter separating the emulsion layers from the image-receiving layers and superposing the latter with the images in registration. Photographic assemblagesor film units adapted to use in this process generally comprise two. sheets, each in: cluding a photosensitive emulsion layer and an imagereceiving layer superposed with the photosensitive layer. The two sheets are attached to one another with the photosensitive layers in face-to-face contact and remain fastened togetherthroughout the process, being fastened in such a manner that the areas thereof adapted to be exposed and treated with fluid reagents may be spaced apart from one another during treatment and topermit the separation of the emulsion layers fromthe imagereceiving layers while assuring accurate registration of the images in the image-receivinglayers when the latter are superposed with one another.

Reference is now made to the drawings, and particular- 1y to Figs. 1 through 4, wherein there is shown a photographic assemblage or film unit of the type described and adapted to the performance of the method of the invention, the relative thicknesses of the materials being exaggerated in some instances forclarity of illustration. The photographic assemblage, designated 10, comprises a pair of sheetlike elements 12 and 22 each comprising a multiplicity of layers or strata carried on a flexible sup port sheet. Sheets 12 and 22 comprise, respectively, support sheets 14 and 24 formed of a transparent and substantially flexible material of the type generally used as a base for photographic film, such as cellulose acetate, cellulose triacetate or other organic plastic materials. Support sheets 14 and 24 carry, respectively, image receiving layers 16v and 26, stripping layers 18 and 28, and photosensitive emulsion layers 20 and 30, stripping layers 18 and 28 being located between the image-receiving layers and the emulsion layersto provide for the separation of the emulsion layers from the image-receiving layers which are adapted to remain on the support sheets in the finished print. If the finished print is to be of the type adapted to be viewed in reflected light, rather than a transparency, one of support sheets 14 and 24 (here sheet 24) could be of an opaque material such as paper or the like so, long as the other support sheet registered with one another even though the sheets are spaced apart during processing. In the form shown, this last-mentioned means for fastening sheets 12 and 22 together comprises a hinge 32 secured to one edge of the sheets, permitting the areas thereof which are exposed and treated to be spaced apart, yet prohibiting lateral movement of the sheets relative to one another. Fastening of the sheets together in this manner, it will be noted, also permits them to be spaced apart, if desired, during exposure while retaining the advantages of predetermined registration. Other conventional fastening means useful for securing sheets together are suitable for the purposes for this invention and include, for example, staples, rivets stitching, cementing and the like. Alternatively, support sheets 14 and 24 could comprise sections of a single sheet folded intermediate its ends.

Spreading of the fluid reagents on sheets 12 and 22 is effected with the aid of a flat sheet or plate 34 which is introduced between the sheets so that emulsion layers (here sheet 14) is transparent, since the imageis intended to be formed in layers-located on and between the superposed support sheets.

Sheets 12 and 22 are superposed with one another with the emulsion layers 20 and 30 in intimate face-to-face contact so that the two emulsion layers can be exposed simultaneously, one through the other, while both layers are maintained in intimate contact. The two emulsion layers include generally coextensive areas adapted to be exposed and. the two sheets .12 and 22 are fastened together adjacent one edge of these areas in such a manner that the images formed in the two sheets may be easily 20 and 30 are in superposition with opposite surfaces of the plate. Plate 34 is substantially rigid, as compared to sheets 12 and 22, and is at least sufficiently inflexible to resist deformation due to differences in hydraulic pressure generated within the layers of fluids as they are spread on opposite sides of the plate. Accordingly, plate 34 may be considerably thicker in section than sheets 12 and 22' and is formed, for example, of sheet metal or organic plastic materials having substantial structural strength and rigidity. One end of plate 34 may be tapered, as shown, to facilitate introduction of the plate between the sheets and the other end may be suitably formed so as to aid in trapping any excess of the fluid reagents.

Reference is now made to for simultaneously spreading two layers of fluid between the sheets on opposite sides of plate 34, together with a pair of pressure-applying members between which the sheets and plate are moved. In the form shown, the pressure-applying members comprise a pair of elongated rolls 36 and 38 having intermediate cylindrical portions defining fluid-spreading surfaces. Roll 38 is mounted for rotation on a pair of stubshafts 40 located at its ends journaled in a suitable support or frame 42 which may comprise a portion of photographieapparatus, such as a camera. its ends mounted for rotation on a pair of movable support members 46 so that roll 36 is movable'towa-rd and away from roll 38. Resilient means in the forrriof springs 48 are provided for urgingroll '36 toward roll 38. While the pressure-applying members have been shown as comprisinga pair of rotatably mounted, cylindrical rolls, other formsof the invention contemplate theuse of nonrotatable pressure-applying members having convergent fluid-spreading surfaces. Considered to be within the scope of the invention are types of substantially rigid members having fluid-spreading surfaces which converge toward one another and are straight in the direction of their elongation. The fluid-spreading surfaces of the presrolls shown. In the preferred form of the invention, the

pressure-applying members are held stationary while the sheets are moved therebetween. However, it is possible to spread the fluid by holding the sheets stationary and moving the pressure-applying members.

In the form 'shown, the aforementioned edge-engaging portions of the pressure-applying rolls comprise a pair of steps or raised shoulders on the ends of each roll having a diameter greater thauthe intermediate portions of the roll. These steps on the ends of rolls 36 and 38 are'designated 37 and '39, respectively, and are positioned to engage theedges of sheets '12 and 22 and plate 34 superposed therebetween for spacing the fluid-spreading surfaces of the rolls apart by an'amount predeterminedly Figs. 2 through 5 of the drawings wherein there is illustrated a preferred method Roll 36 includes a pair of stub shafts 44 at if greater than the combined thickness of the edge portions of the sheets and plate. The height of the shoulders on each roll or the difference between the radius of the shoulders and the fluid-spreading surfaces therebetween approximates the thickness of a layer of fluid to be spread thereby between one of the sheets and a surface of plate 34. In one preferred form of the invention, the height ofeach pair of shoulders ranges between two and six thousandths of an inch and controls the spacing between the fluid-spreading surface of a roll and a surface of plate 34, so that it remains greater than the edge thickness of the sheet located therebetween by a constant amount which is substantially equal to the height of the shoulders, this amount remaining substantially constant despite variations in the thicknesses of the sheets and plate.

Plate 34, located between sheets 12 and 22, functions in the nature of a pressure-applying member in that each surface of the plate acts as one of a pair of fluid-spreading surfaces, the other of the pair of surfaces comprising one of the rolls. Plate 34, being substantially rigid, is not easily deformed due to hydraulic pressure generated in the fluid layers so that the thickness of each layer is a function of the height of the shoulders on one of the rolls. Accordingly, by providing rolls with shoulders of different heights, it is possible to spread two fluids simultaneously in layers of different thickness and and the thicknesses of said layers can be accurately predetermined and maintained uniform. Another feature of having shoulders on the rolls is that the shoulders exert increased pressure at the margins of the sheets, tending to confine the fluids between the sheets and prevent their escaping from between the margins of the sheets as the fluids are being spread.

The fluid reagents may be provided between the sheets in a'variety of ways and, in a preferred form of the invention, are provided in a pair of elongated rupturablc containers t adapted to rupture and discharge their fluid contents in one direction when subjected to compressive pressure during advancement between a pair of pressureapplying mernlbers. Containers of the preferred type may be formed, for example, by taking a single sheet of fluidimpervious multilayer material and folding the same medially, and thereafter securing the end marginal portions and the longitudinal portions of the two folded faces to one another, providing a central cavity for containing the fluid reagent. The longitudinal. seal between the marginal portions is preferably such that, upon application of a predetermined force to the walls of the container, there may be created within the container a sufficient hydraulic pressure to separate the marginal portions throughout substantially their entire length. In the form shown, con tainers 50, each carrying a quantity of fluid indicated at 52, are secured to opposite sides of plate 34- adjacent the tapered end thereof adapted to be introduced between sheets 12 and 22. This arrangement is preferable to securing the containers between the sheets since, in this arrangement, the containers do not interfere with the registration of the two sheets when they are superposed.

Following exposure of the photosensitive layers and an assemblage it} disposed, for example, as shown in Fig. 1, treatment of the photosensitive layers with fluid reagents is effected by introducing a plate 34, carrying a pair of fluid-filled containers 5%, between sheets 12 and 22 with the containers located adjacent hinge 32 substantially in the manner shown in Fig. 2. Thereafter, the sheets and plate are moved in superposition between rolls 36 and 38, commencing at the end adjacent the containers, for spreading each of'fiuids 52 in a layer 54 between one of the sheets and-a surface of plate 34 toform a sandv lich.

The plate, being rigid, may be employed to advantage for I pushing the assemblage between the rolls or the assemblage maybe drawn between the rolls or advanced therebetween in response to rotation of the rolls. Following spreadingof the fluids, the sheets are allowed to remain in superposed relation during a predetermined processing period, at the end of which each of the sheets may be stripped from the plate, the plate withdrawn from between the sheets and the two sheets superposed again in their original position. The containers are preferably attached to the plate so that they remain with the plate when it is withdrawn from between the sheets. Also, as previously mentioned, emulsion layers 26 and 30 are intended to be stripped from image-receiving layers 16 and 26 and this may be accomplished by causing the emulsion layers to adhere to the plate as the sheets are stripped therefrom.

The cooperating portions, which act to space apart the fluid-spreading surface of each roll and the surface of the rigid plate, may be provided on the plate itself as marginal shoulders or strips on either or both surfaces of the plate. Such an arrangement would find added utility, for example, when it is desired to simultaneously'spread three separate layers of fluid reagents, as shown in Fig. 6 of the drawings. The three layers of fluid, designated 61, 63 and 65, are spread, respectively, on three sheets 60, 62 and 64 with the aid of two rigid plates 66 and 68 and a pair of pressure-applying rolls 70 and 72. Each of rolls 70 and 72 includes a pair of raised shoulders, designated respectively 71 and 73, at its ends substantially as shown and previously described and one of the plates, here plate 6 8, is provided with a pair of raised shoulders 69 at its lateral edges.

The sheets 60, 62 and 64 may be of any desired nature and composition and, for example, sheets 68 and 62 may be similar to sheets 12 and 22 and adapted to record two portions of the spectrum while sheet 64 may be adapted to record a third portion of the spectrum so that the as semblage of the three sheets may be used in the production of an image in terms of three colors or dyes. 'Plate 66 is substantially flat and without shoulders and is located between sheets 6d and 62. Shoulders 71 on roll 70 cooperate with plate as to control the thickness of layer 61 of fluid spread between sheet 6ft and the surface of plate 66. Plate 625 is located between sheets 62 and 64 with shoulders 69 in contact with sheet 62 so that they cooperate, with plate 66 to control the thickness of the layer 63 of fluid spread between the other surface of plate 66 and sheet 62. The surface ofplate 63 located adjacent sheet 64 is plane and shoulders 73 on roll 72 cooperate with plate 63 to control the thickness of the spread of fluid in layer 65 between sheet 64 andplate 68. Y

The three sheets 6%, 62 and 4 may be fastened together and exposed while in superposition, although it is apparent that only two of the photosensitive layers (on sheets 69 and 62) would be in contact with one another. The plates would be provided with containers of fluid, one of the plates mounting two containers and the other plate mounting one container. The two plates would be introduced between the sheets to commence the treatment of the sheets and would be withdrawn'frorn between the sheets at the end of the treatment, at which time the photosensitive layers could be stripped from the sheets, for example, by adhering them to the plates. The three sheets, each preferably carrying an image, could then be superposed with two of the image-carrying layers in contact with one another and with the third layer spaced from the other two by the thickness of one of the sheets whereby the three images could be viewed in conjunction with one another.

Generally, fluid processing reagents useful in the performance of the invention include a fihn-forming material which is preferably a high molecular weight polymer and which imparts to the fluid agent a predetermined high viscosity. A high viscosity for the fluid processing agent is very desirable since it makes possible the relatively uni form spreading of the fluid agent and insures a complete coverage of the desired area by said agent. The fihnforming material is preferably contained in thefiuid agent in suitable quantities to impart thereto a viscosity in excess of lOOOcentipoises at a temperature of 24 C. and pref 9 erably of the order of 1000 to 200,000 centipoises at said temperature. a

The film-forming material is preferably of such character as to retain its viscosity-imparting and film-forming properties in an aqueous alkaline solution so that the fluid agent, once its ingredients have been mixed 'and have attained an equilibrium, remains uniformly viscous for any given temperature for long periods of time. The film-forming material is. preferably one of the class of high molecular weight polymers which include, in their chemical structure, such groups as, for example, the ether, alkyl, hydroxyl, carboxyl and acetyl groups that are stable to alkalies and .which contain chemical groups, such as the ester and acid chloride groups, that are stable to alkalies. The polymers also contain groups, such as the hydroxyl and/or carboxyl groups, which tend to solubilize the polymer in aqueous alkaline solution. Suitable examples of such polymers are the alkali-inert and water-soluble cellulose derivatives such as sodium carboxymethyl cellulose and hydroxyethyl cellulose and the alkali-inert and water-soluble polyalkane derivatives such as polyvinyl alcohol and the sodium salts of polymethacrylic and polyacrylic acid.

Fluid processing compositions adapted to be spread 'in a thin layer between an exposed silver halide emulsion layer and a rigid plate to effect the formation of a dye image in an image-receiving layer underlying 'the emulsion layer preferably contain color-providing substances. The expressioncolor-providing substances, as used herein, is intended to include all types of substances or reagents which may be utilized to produce a positive image in terms of a dye. The chromophoric system imparting the desired color properties to the positive image dye may be initially contained in such colorproviding substances or such chrornophoric system may be formed as a result of a reaction after transfer, such as oxidation and/or coupling. Thecolor-providing substance initially may be of the same color as the inrage dye to be produced thereby or may be of a different color or a :neutral color. Such color-providing substances do not form a part of the inventive subject matter, .of this application and therefore are not given in 'detail.' For purposes of illustration, however, Jmention may be made of the following types of color-providing substances which may be utilized in employing the inventive concepts of this invention.

1) Color formers or couplers which react with the oxidation product of color developers to produce a dye; see for example the following patents issued to Edwin Land; 2,559,643, issued July 10, 1951, 2,661,293,

issued December l, 1953, 2,698,244, issued,-December 28, 1954, and 2,698,798, issued January 4,,1955. (2) Self cou'pling developers, e.g., a silverihalide developing agent, capable ,of 'coup1ing with itself, iwhen oxidized, to form a dye; see for examplejthe above mentioned Patent'No. 2,698,244.

(3) Dye developers, thatis, gcor npletedyeswhich' possess a silver halide developingfunction; see forl jexample the copending applica'tion of Howard G,; Rogers Serial No' 415,073, filed-March 9,;1954,inow, abandoned."

(4) Leuco dyes, that is, dyes utilized in their leucopr reduced form and'which possess a silver; halide developing functionfbut which must be"oxid ized after transfer the imageireceiving material; see for example-the cop'endingf applicationiof Howard G. Roger'sfserial No. x

464,175, filed October 22 ,-[19 54'.

, (5) Coupling dyes, i.e.,' acomplete dye which is halide emulsion layer containing a latent color record imageis processed by a fluid reagent to obtain an imagewise distribution of diffusible color-providing substances. The imagewise distribution of difiusible color-providing substances results from immobilization or trapping of color-providing substances in exposed areas in situ with the developed silver as a result of the development of the latent image. A positive image may be obtained by the transfer of such diifusible nonimmobilized color-providing substances by imbibition from the developed photosensitive layer to a superposed image-receiving layer. The desired image is then revealed by stripping the developed photosensitive layer from the image-receiving layer after a suitable imbibition period.

The preferred color-providing substances are dye developers and the desired imagewise distribution of diffusible dye developer results from the immobilization of the dye developer oxidized in developing the latent image.

An example of an aqueous fluid processing composition including a dye developer as the color-providing substance is given, by weight, as follows:

' Percent Sodium carboxymethyl cellulose (high viscosity) 4.5 Sodium hydroxide 2 Potassium bromide 0.2 1-phenyl-3-pyrazolidone 0.2 7 Sodium carbonate 2 Dye developer 6 The percentage of dye developer given above is merely illustrative and may range, for example, depending on the particular developer employed, between 2 and 12%. Suitable 'dye developers for use in the above-described fluid processing composition are:

For yellow:

2-naphthylazohydroquinone 1-phenyl-3-methy1-4-[p-(2,5 dihydroxyphenethyl)- phenylazo1-5-pyrazolone 1 1-phenyl-3-cyclohexyl carboxamido-4-[p-(2',5'-dihydroxy-phenethyl) -phenylazo] -'5-pyrazolone I Phenylazohydroquinone For magentaz' 2-hydroxynaphthylazohydroquinone '2 [p (2',5' dihydroxyphenethyl) phenylazo1-4- methoxy-l-naphthol 1-arnino-4-phenylazo-2-naphthol For cyan:

I 1,4 bis [f3 (2,5-dihydroxyphenyl) ethylamino]- anthraquinone e m u i r a In the performance of the invention, as illustrated in Fig. 3, two layers of fluid processing reagents, prepared in accordance with theforegoing example and containing dye developers'of the desired colors such'as cyan and magenta,

:-are spread between sheets. 12 and 22 and oppositelsurfaces posure of the superposed photosensitive layers is adapted capable of coupling wiaijhe oxidation product qf a 'cplor developer, e. g., diethylipararphenyl tediamine, to

1 form an im mooile dye; see for example' the.,copending application. of Howard Ra es, Serial No. ,.35 8,012 .1953, now,U.S. Patent' No."2,'7j4 668. In drif transfer-reversal processe f,

lve

to be madethrough sheet 12 and, accordingly, support sheet 24. is provided with a suitable anti-halation coating, 7

. designated 24a. TIn an alternative embodiment wherein it :is desired'to produce a'positive'print to be viewed in reflected light, support sheet 24 may comprise one of the 'opaque sheetmaterials generally used as abase for positive prints, such as baryta paper.

Theimage-receiving layers 16 and 26 are of a material substantive to'the dyes employed in the fluid reagent. A

-material:;-suitable for' thi s purpose is DuPont-Type 8 ,lslylon (trade name ,for. N-me'thoxy methyl .polyhexam e y ene a pami e). ay at this m terial may be M f 1,4 bis 3-(2,5'-dihydroxyphenyl)-propylamino]- .formediby coating a solution using "ethyl alcohol "'as *a SO'lVeBt. 'I oLfacilitateand insure adherence of'the'imageereceiving layersto the support.sheets,"there are-prowided subcoats, designated 16a and 26a, .on the: support :sheets comprising polyvinyl butyral.

intimate contact with one another for recording different aspects of the subject without the'aid of filters.

As previously mentioned, the silver halide emulsion layers are intended to be stripped from the :imageqeceiv- 'ing layers when treatment is complete. T o facilitate'stripplug of photosensitive emulsion layers and 30, there are provided stripping layers 18 and ZS'betWeen the emulsion layers and the image-receiving layers. Stripping layers 18 and 28 are of a material which is soluble in, or atleast softened by, thefiuid reagents, such materials as hydroxyiethyl cellulose and cellulose acetate hydrogen phthalate being suitable'for this purpose. Stripping layers 18 and 28 may be prepared by coating an aqueous solution comprising, by weight, 2% hydroxyethyl cellulose and 2% sugar on the image-receiving layers. The film-forming materials in the layers of fluid reagents tendto solidify as the'fluid is absorbed into the sheets or evaporates fromthe layers and, as the materialsolidifies, causes'the photosensitive emulsion layers to be adhered to the rigid plate. The

photosensitive layers are adhered to the plate with a greater afiinity than to the image-receiving layers when the stripping layers have been dissolved or softened, with the result that, as the sheets and plate are stripped apart,

the emulsion layers are stripped along with the plate from the image-receiving layers. The plate may be provided with a coating of a material which is substantially nonsubstantive to the dyes employed and, for the purposesof the present invention, is preferably polyvinyl alcohol.

.As previously intimated, the color-providing sub-stances, preferably dye developers, may be provided other than in the fluid reagent; for example, they may be'provided in one of the layers comprising each of'the sheets or as layers on the surfaces of the rigid plate. It is possible to'apply the dye developers to the surfaces of the rigid plate by coating the plate with gelatin and applying each developer to the gelatin in a solution of 4%, by Weight cellulose acetate hydrogen phthalate in 50-50 by volume of ace tone and tetrahydrofuran.

Other color processes may be performed by the method of the invention employing a modified form of the hereindescribed photographic assemblage. For example, instead of producing two or more monochrome images, one of the photosensitive elements may include a screen type of sturcture for producing two or more subtractive, color records :as described in my copending application Serial No. .448,44'l, filed August 9, 1954, now US. Patent 2,968,554, issued January 17,1961, while the other photosensitive element is so constituted as to produce a monochrome accord in a'third color substantially as described.

' In another form, one of the photosensitive elements may be constructed and processed in accordance'with my copending joint application with Howard G. Rogers, Serial No. 565,135, filed February 13, 1956, wherein there is described the structure of a photosensitive elementtcomprising two or more differently sensitized emulsion layers superposed with one another, each emulsion layer being sensitized preferably for one of the primary colors and containing a color-providing substance for providing an image in terms of a dye of the complementary color.

While the photosensitive layers have been shown and described as preferably comprisingsilver halide emulsions and-the fluid reagents as comprising materials fo'r'p'roduc- :jngpositive images in terms of dyes, the 'pre'sent'int/ention may'find' equal utility in the performance of photographic processes employing other photosensitive materials and/ or reagents. For 'example, the fluid processing reagents may 1 2 be -adapte'cl-to the production off-positivesilver images by diffusion transfer-reversal and may comprise 'a silver halide developer such as hydroquinone, a silver halide solvent such as sodium thiosulfa'teyand 'an alkali. Fluid reagents ofthis typeare adapted to developth'e exposed isilver halide to'silver and to form from unexposed silve'r halide a'soluble silver complex whichmay be transferred by-imbibition to the image-receiving layer where it is reduced to silver to form a positive print.

The photographic processes and various species of :fluid processing reagents of the above type, useful in the :production of-silver images by diffusion transfer-reversal :processes, are further described in US. Patent No.

ever, in processes wherein it is desirable to produce amages in terms of silver, the image-receiving layers preferably contain certain materials whose presence during a silver halide diffusion transfer-reversal process have a desirable effect on the amount and character ofthe silver precipitated during print formation. This layer, which preferably provides a vigorous silver precipitating environment, contains silver precipitating nuclei of the type described Patents Nos. "2,698,237 and 2,698,245, both issued to Edwin H. Land on December 28, 1954, dispersed i-n a'macroscopically continuous vehicle including Water-impermeable, inorganic, preferably siliceous material. This layer may-contain, for example, one of the absorbent siliceous materials such as oxides of silicon like silica aerogel, mica and talc, and one of the'metallic sulfides and selenides, thiooxalates, thioacetamides, and colloidal metals, specifically colloidal silver.

In another modification of the film unit and fluid reagents, for example, the photosensitive layers may comprise photosensitive ferric salts which, when photoexposed, are capable of being reduced to ferrous salts. Suitable photosensitive ferric salts include ferric chloride and ferric salts of organic acids, such as ferric oxalate, ferric tartrate and ferric citrate. The fluid processing reagents would preferably include couplers which differentiate between ferric and ferrous salts to form visibly distinguishable reduction products with one or the other. Examples of such couplers are potassium ferricyanide, potassium ferrocyanide, the tannins, B-naphthoquinone sulfonic acid, silver salts, platinum and palladium salts, and various colloid materials such as gelatin andfgu'm arabic.

In a further modification of the filmunit shown, the photosensitive layers may include photosensitive 'diazomum compounds, while the fluid reagents may include couplers capable of combining with exposed or unexposed :diazonium compounds to form visibly distinguishable dyes; or the couplers may be provided in the photosensitive layers or otherlayers associated therewith, while the fluids merely provide environments in which the coupling reactionsv may occur. Suitable photosensitive drazomum compounds, for example, may be prepared by treating aromatic amines with nitrous acid'at low temperature and, as suitable couplers, mention may be made of phenols, naphthols and amino compounds.

Qth'er materials which may find utility in the photosensrtrve layer include materials which are differentially 'solubi'lized by exposure t'o'light and include, for example, dichromated gelatin and the like; V

The emulsionlaye'r'sjw and- 30 of sheets '12 and 22, respectivelyfmay be coextensive with the entire inner Surface of each "ofthe sheet' sfia's shown in Fig. 2)

n that the emulsion layer is also'present in the region where 'no processinguoccur's, that is, in the region of containers -50. "l'n'jthis case the portions ofthe emulsion layersiii this region may 'not be stri ped fm g image r eb;iving layers and may remain 'betweenthe two sheets.

estates- 13 j v the thickness of the emulsion layers is relatively small; this makes no appreciable difference in the thickness of or the registration of the images in the finished product. Alternatively, the sheets may be provided without photosensitive layers in the region of the containers'where no processing occurs so that the finished product, after processing is complete and the processed emulsion layers have been stripped therefrom, may contain no emulsion layer substantially as shown in Fig. 4.

Since certain changes may be made in the above product, process and apparatus without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. A method of simultaneously treating at least two exposed photosensitive material layers arranged in facing relation and each including a latent photographic image and each comprising at least a portion of a substantially flexible sheet, with at least two fluid processing agents to produce two visible photographic images said method comprising introducing a substantially inflexible sheetlike element between said flexible sheets in superposition with said exposed photosensitive layers, the latter being dis-,

posed innermost adjacent said element, said element be-.

ing substantially less flexible than said sheets; providing a quantity of one of said fluid agents between each of said photosensitive layers and a surface of said element, each of said fluid agents being capable when permeated into one of said photosentitive layers of developing th'e latent image therein to produce a visible image on said sheet comprising said one photosensitive layer; 'moving said sheets and said element in superposed relation relative to and between a pair of pressure-applying members each having a fluid-spreading surface portion juxtaposed with the other and a pair of cooperating portions on opposite sides of said fluid-spreading surface portion; during movement of said sheets and said element between said pressure-applyingmembers, causing each of said pairs of cooperating portions of each of said members to engage one of said sheets and space apart said fluidspreading surface portion of said each member and a surface of said element by an amount predeterminedly greater than the thickness of said one sheet located therebetween and deforming each of said sheets between said element and one of said pressure-applying members to provide a space between said each sheet and a surface of said element; spreading one of said fluid processing agents in a thin layer of predetermined thickness within said space between said each sheet and a surface of said element for permeation into one of said photosensitive layers; thereafter maintaining said sheets and said element in superposition with said layers of fluid located between said sheets on opposite sides of said element for a processing period of predetermined duration, during said processing period, reacting said fluid with said photosensitive layer to form a visible transfer image in a layer comprising each of said sheets; the last-mentioned layers being located exterior of the sandwich comprising said element and said photosensitive layers and, at the end of said period, withdrawing said element from between said sheets and said last-mentioned layers containing said visible images and removing said photosensitive layers from said last-mentioned layers and from between said sheets.

2. The method of claim 1 wherein at least said lastmentioned photosensitive layer comprises a silver halide emulsion, and the last-mentioned fluid processing agent includes a substance selected from the class consisting of the silver halide developers and a substance selected from the class consisting of the silver halide solvents.

3. A method of simultaneously producing two visible photographic images in registration with one another, which method comprises superposing two sheets, each 14 including a photosensitive layer, with said photosensitive?- layers in face-to-face contact with one'another and simul-' taneously exposing said photosensitive layers to produce latent photographic images in said photosensitive layers; introducing between said sheets a sheetlike element which is substantially less flexible than said sheets and has attached to its opposite surfaces at least two rupturable containers each holding a quantity of a fluid composition 'capable, when permeated into one of said photosensitive layers, of developing the latent image in said one photosensitive layer and producing, as a result of development of said latent image therein, an imagewise distribution of transferable image-forming substances; superposing each of said photosensitive layers with one of said surfaces of said element; moving said sheets and said element in superposition together with said containers relative to and between a pair of pressure-applying members, each having a fluid-spreading surface portion juxtaposed with the other and cooperating portions on opposite sides of said fluid spreading surface portion, for spreading said fluid compositions from said containers in substantially uniformvlayers between and in contact with eachof said photosensitive layers and said element for permeation into the photosensitive layers; during movement of said sheets and said element between said pressure-applying members, causing each of said pairs of cooperating portions of each of said members to engage one of said sheets and space apart said fluid-spreading surface por-' tion of said each member and a surface of said element by an amount predeterminedly greater than the thickness 'of said one sheet located therebetween and deforming each of said sheets away from said element while thelatt'er remains substantially unde-formed to provide spaces between said sheets and the surfaces of said ele menti within which said fluid. compositions are spread; thereafter maintaining said sheets and said element in superposition with said layers of fluid located between said sheets on opposite sides of said element for a processing period of predetermined duration said processing period developing said latent images, forming imagewise distributions of transferable image-forming substances and transferring said image-forming substances by diffusion from each of said photosentitive layers to an imagereceiving layer comprising the same sheet as saideach photosentitive layer to form a visible transfer image in said image-receiving layer; during said image-receiving layers being located exterior of the sandwich comprising said element and said photosentitive layers; at the end of said period, withdrawing said element from between said sheets, removing said photosensitive layers from said image-receiving layers and superposing said sheets and said image-receiving layers with said visible transfer images in registration with one another. I

4. The method of claim 3 wherein said photosensitive layers comprise silver halide emulsions having different color sensitivities, said visible images comprise dyes, said fluid compositions include substances selected from the class consisting of the silver halide developers and said image-forming substances produced by said fluid compositions as a result of development of said latent images comprise color-providing substances selected from the glass consisting of said dyes and intermediates for said yes. 1

5. A method .of forming at least two photographic images comprising two sheets fastened to one another and each including superposed photosensitive and image-receiving layers, said sheets being arranged with said photosensitivelayers in face-to-face contact; while maintaining said sheets'secured together and while holding said photosensitive layers in intimate face-to-face contact, simultaneously exposing said photosensitive layers to produce therein at least two different latent images of a subject; separating said exposed photosensitive layers from one another and while maintaining said photosensitive layers separated from one another, providing quantities of fluid sides of an'intervening layer, said fluid agents 'being' capable, when permeated into each of said photosensitive layers, of developing the latent image therein and forming, as a result of said development, an imagewise. distribution of transferable image-forming substances; spreading said fluid agents in separate layers against opposite sides of said intervening layer on each of said photosensitive layers for permeation into said each photosensitive layer; by said layers of fluid developing said latent images, forming transferable image-forming substances in said photosensitive layers and transferring said image-forming substancm from each of said photosensitive layers to the image-receiving layer superposed therewith to produce in the last-mentioned image-receiving layer a visible transfer image; said image-receiving layers being located exterior of the sandwich comprising said intervening layer and said photosensitive layers; thereafter, withdrawing said intervening layer from between said image-receiving layers; stripping said photosensitive layers from said image-receiving layers; and superposing said sheets with said image-receiving layers in intimate face-to-face contact, at least one of said sheets being transparent to permit exposure of said photosensitive layers and exhibition of the transfer images in said image-receiving layers.

6. The method of claim 3 wherein at least one of said photosensitive layers comprises at least two photosensitive silver halide emulsions each having a peak sensitivity within a dilferent portion of the visible Wavelength range and the other of said photosensitive layers comprises a photosensitive silver halide emulsion having a peak sensitivity within a portion of said Wavelength range difierent from the peak sensitivity of the first-mentioned silver halide emulsions; said images comprise dyes; and said transferable image-forming substances comprise colorproviding substances initially incorporated in each of said emulsions, the color-providing substance incorporated in each of said emulsions comprising a material selected from the class consisting of said dyes and intermediates for said dyes, the colorof each of said dyes being thesubstantial complement of the color for which the parsaid photosensitive layers and the surfaces of said ele-:

ment and are spaced in contact with said photosensitive layers for permeation into said photosensitive layers by movement of said sheets and element in superposition rel-- ative to and between a pair of juxtaposed pressure-applying members; said photosensitive layers are caused by said layers of fluid agents to be adhered to the surfaces of said element with a greater afiinity than to the imagereceiving layers with which said photosensitive layers are superposed during withdrawal of said element from between said sheets, whereby said photosensitive layers are stripped from said image-receiving layers by withdrawal of said element.

References Cited in the file of this patent UNITED STATES PATENTS 2,565,378 Land Aug. 21, 1951 2,647,049. Land July 28, 1953 2,686,716 Land Aug. 17, 1954 2,740,341' McCune Apr. 3, 1956 :UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,977,226 Y March 28, 1961 Edwin Land It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 40, for "Hithertofore" read Heret'ofore column 10, line 37, for "2 ,5-dihydroxyphenethyl" read 2 ,5 dihydroxyphenethy1 column 14, line 39, for "duration said processing" read duration during said processing line 45, strike out "during"; column 16, line 16, for "spaced" read spread Signed and sealed this 19th day of March 1963.

(SEAL) Attest:

ESTON G, JOHNSON DAVID L. LADD Attesting Officer j Commissioner of Patents 

1. A METHOD OF SIMULTANEOUSLY TREATING AT LEAST TWO EXPOSED PHOTOSENSITIVE MATERIAL LAYERS ARRANGED IN FACING RELATION AND EACH INCLUDING A LATENT PHOTOGRAPHIC IMAGE AND EACH COMPRISING AT LEAST A PORTION OF A SUBSTANTIALLY FLEXIBLE SHEET, WITH AT LEAST TWO FLUID PROCESSING AGENTS TO PRODUCE TWO VISIBLE PHOTOGRAPHIC IMAGES SAID METHOD COMPRISING INTRODUCING A SUBSTANTIALLY INFLEXIBLE SHEETLIKE ELEMENT BETWEEN SAID FLEXIBLE SHEETS IN SUPERPOSITION WITH SAID EXPOSED PHOTOSENSITIVE LAYERS, THE LATTER BEING DISPOSED INNERMOST ADJACENT SAID ELEMENT, SAID ELEMENT BEING SUBSTANTIALLY LESS FLEXIBLE THAN SAID SHEETS, PROVIDING A QUANTITY OF ONE OF SAID FLUID AGENTS BETWEEN EACH OF SAID PHOTOSENSITIVE LAYERS AND A SURFACE OF SAID ELEMENT. EACH OF SAID FLUID AGENTS BEING CAPABLE WHEN PERMEATED INTO ONE OF SAID PHOTOSENSITIVE LAYERS OF DEVELOPING THE LATENT IMAGE THEREIN TO PRODUCE A VISIBLE IMAGE ON SAID SHEET COMPRISING SAID ONE PHOTOSENSITIVE LAYER, MOVING SAID SHEETS AND SAID ELEMENT IN SUPERPOSED RELATION RELATIVE TO AND BETWEEN A PAIR OF PRESSURE-APPLYING MEMBERS EACH HAVING A FLUID-SPREADING SURFACE PORTION JUXTAPOSED WITH THE OTHERAND A PAIR OF COOPERATING PORTIONS ON OPPOSITE SIDES OF SAID FLUID-SPREADING SURFACE PORTION, DURING MOVEMENT OF SAID SHEETS AND SAID ELEMENT BETWEEN SAID PRESSURE-APPLYING MEMBERS, CAUSING EACH OF SAID PAIRS OF COOPERATING PORTIONS OF EACH OF SAID MEMBERS TO ENGAGE ONE OF SAID SHEETS AND SPACE APART SAID FLUIDSPREADING SURFACE PORTION OF SAID EACH MEMBER AND A SURFACE OF SAID ELEMENT BY AN AMOUNT PREDETERMINEDLY GREATER THAN THE THICKNESS OF SAID ONE SHEET LOCATED THEREBETWEEN AND DEFORMING EACH OF SAID SHEETS BETWEEN SAID ELEMENT AND ONE OF SAID PRESSURE-APPLYING MEMBERS TO PROVIDE A SPACE BETWEEN SAID EACH SHEET AND A SURFACE OF SAID ELEMENT, SPREADING ONE OF SAID FLUID PROCESSING AGENTS IN A THIN LAYER OF PREDETERMINED THICKNESS WITHIN SAID SPACE BETWEEN SAID EACH SHEET AND A SURFACE OF SAID ELEMENT FOR PERMEATION INTO ONE OF SAID PHOTOSENSITIVE LAYERS, THEREAFTER MAINTAINING SAID SHEETS AND SAID ELEMENT IN SUPERPOSITION WITH SAID LAYERS OF FLUID LOCATED BETWEEN SAID SHEETS ON OPPOSITE SIDES OF SAID ELEMENT FOR A PROCESSING PERIOD OF PREDETERMINED DURATION, DURING SAID PROCESSING PERIOD, REACTING SAID FLUID WITH SAID PHOTOSENSITIVE LAYER TO FORM A VISIBLE TRANSFER IMAGE IN A LAYER COMPRISING EACH OF SAID SHEETS, THE LAST-MENTIONED LAYERS BEING LOCATED EXTERIOR OF THE SANDWICH COMPRISING SAID ELEMENT AND SAID PHOTOSENSITIVE LAYERS AND, AT THE END OF SAID PERIOD, WITHDRAWING SAID ELEMENT FROM BETWEEN SAID SHEETS AND SAID LAST-MENTIONED LAYERS CONTAINING SAID VISIBLE IMAGES AND REMOVING SAID PHOTOSENSITIVE LAYERS FROM SAID LAST-MENTIONED LAYERS AND FROM BETWEEN SAID SHEETS. 